The present invention is directed to a device and associated method for bypassing the control of a non-redundant module, such as a network controller, when that module is sensed to be operating improperly. Recently, telephony has begun to use what are known as add/drop multiplexers (ADM's) whose function is to add or remove telephony channels from a high speed multiplexed telephony communication highway. For example, the add/drop multiplexer may be associated with high speed east and west ports (the terms "east" and "west" are commonly used in telephony with respect to describing communication direction) associated with a high speed channel operating at 51.84 megabits per second. This high speed channel may conform to the synchronous optical network (SONET) standard for use in fiber optics interfaces or may conform to such a standard with an electrical interface.
In either event, the add/drop multiplexer further comprises a plurality of lower speed channels such as channels conforming to the DS-1 standard; that is channels (also called links), operating at 1.544 megabits per second. Each DS-1 channel can further comprise up to 24 lower speed channels such as 64 kilobit per second DS-0 channels so that in effect, the high speed channel multiplexes the DS-1 channels which in turn multiplex lower speed DS-0 channels.
The add/drop multiplexer is therefore particularly designed to add or remove DS-1 channels from the high speed channel and to pass these channels along with other through channels via the high speed channel downstream. Such add/drop multiplexers typically incorporate a network element controller which provides performance monitoring, control, alarm reporting, and provisioning of the network element. In particular, the network element controller is responsible for provisioning the time slot multiplexer which in turn provides the ability to crossconnect any synchronous transport signal (STS) virtual tributary (VT) as well as any DS-1 add/drop link. If the network element controller is not of a redundant type, its failure would prevent the proper passage of data communication information between he east and west interfaces of the add/drop multiplexer. It is especially desirable that if the network controller fails, that the SONET section data communication channel information pass through the ADM and thus avoid the network controller.
In particular, the craft orderwire alarm module (COA) of the present invention include circuitry which can detect the status of a watchdog timer which in turn monitors the performance of a network controller. Upon timeout of the watchdog timer, the COA reprovisions the ADM's time slot multiplexer so that the section datacom channel is connected through the east-west high speed interfaces. The watchdog timer also disables the microprocessor associated with the network controller so as to prevent its interference with the TSM.
No prior art device is known which allows use of a non-redundant network controller in association with an add/drop multiplexer so as to allow specified channels within the high speed channel (such as section data communication information) to be passed through the ADM upon perceived failure of the network controller.